I know its frustrating when you trust your fish store to give you good advice

MOST of us have been there and its not a good feeling..but you can make it better and more enjoyable as a hobby and it sounds like you are on the way to do that!!..once the loach, angel and shark are rehomed, I would get a nice school of cardinals or neons (6-8) and mayeb 4 more barbs...then have your bn for the bottom..with some tall plants I think that would be an amazing tank
.again tho do you know the unnamed fish yet?